A two-sided ring-spinning machine with a bobbin-changing apparatus for simultaneously changing full bobbins for empty ones on both sides of the machine has a pair of gripper beams each moved by a respective push/pull member via a respective scissor linkage to grab the full and empty bobbins on each side of the machine.
In order to be able to move this gripper beam in and out and up and down as is necessary for changing the bobbins, each beam is held on a scissor linkage which is pivoted about a shaft in the lower region of the spinning machine or is mounted in a traveling slide. The drive for up-and-down movement of the gripper beam is effected by longitudinal movement of the shaft as described in European patent publication 0,445,375 of W. Klaus or a pull rod mounted in the slide as described in German 2,045,263 or by pulling members as described in German 1,785,217 on the scissor linkage. Electric motors and shaft drives as described in European patent publication 0,445,374 or fluid-powered drive elements as described in above-mentioned German 2,045,263 are used to power the push/pull element.
In commonly owned patent 5,373,689 issued 20 Dec. 1994 a two-sided ring-spinning machine is described having a frame and a pair of parallel spindle banks each holding a respective row of bobbins. A bobbin-changing apparatus has respective gripper beams engageable with the bobbins of the spindle banks, respective scissor linkages pivoted on the frame and on the gripper beams extendable for raising the respective beams and collapsible for lowering the respective beams, and a single force-transmitting element connected to both of the linkages and displaceable longitudinally in one direction for extending the linkages and in the opposite direction for collapsing the linkages. A single drive is connected between the frame and the force-transmitting element for simultaneously vertically displacing both beams.
German patent document 4,210,494 of A. Lattion describes such a scissor-linkage actuator of the above-described general type. It has a spring-loaded vertically effective abutment or bumper onto which the gripper beam comes to rest in its lowered position. This is intended to protect the scissor linkage in its most spread position, when it is least able to gain a mechanical advantage and is under maximum tension. This is an improvement on the system of above-mentioned German 1,785,217 where springs put the scissor arms under enormous stress, but requires a separate element to be provided for this spring support in the lower gripper-beam position. In addition there is a distinct possibility of a machine operator getting pinched between the beam and the element it is coming to rest on, so, to comply with worker-protection regulations, the device must be shielded, again increasing its cost.